Recently, various kinds of printers have been developed and reduced to practice as output devices of computers or printing devices of word processors, and they have contributed to developments of office automations.
The impact printer of a wire dot system uses the wire as the letter forming element for performing printings on a printing paper by selectively striking a platen via an ink ribbon and the printing paper by means of said wire, and has been widely spread, since it is of small size and cheap, and can print many letters, marks, devices and others.